Pregabalin (S-3-Aminomethyl-5-methyl-hexanoic acid) is a 3-substituted γ-amino butyric acid (GABA) analog that exhibits an array of useful medicinal properties, as disclosed in WO 93/23383, as well as U.S. Pat. No. 6,306,910 and WO U.S. Pat. No. 00/76958, the latter two of which are assigned to the same assignee as the instant application. 
Synthetic approaches to pregabalin, its racemate and related analogues such as 3-aminomethyl-5-methyl-octanoic acid, which has the structure generally commence from a linear precursor. For instance, WO 93/23383 discloses a route commencing from 5-methyl-hexanoic acid that requires 8 transformations. A recently disclosed alternative strategy commences with the enantioselective conjugate addition of S-α methylbenzyl amine to 2-Methylene-succinic acid dimethyl ester (Michael J. Mayer, Trip Report, Synthetic Pathways 9thSymposium on the Latest Trends in Organic Synthesis, Albany Molecular Sciences Technical Report Vol. 5, No. 19 (2001), p. 9; also available at http://www.albmolecular.com. logical. net/features/tekreps/vol05 no19/ last visited Feb. 6, 2003). The reaction provides a mixture of diastereomers, which can be separated, and the requisite diastereomer is then converted to pregabalin via 6 additional steps.
A shortcoming of either of these approaches, particularly in scale-up and production contexts, is that they require a multitude of steps and purification operations. As a result, there is a need for a process for synthesizing pregabalin and other 3-substituted γ amino acids that minimizes the total number of synthetic transformations and simplifies purification steps.